The proposed project will use meta-analytic techniques to analyze the effects of brief alcohol interventions on adolescent and young adults' alcohol and other illicit substance use outcomes. By systematically synthesizing research findings on the effects of brief alcohol interventions, the proposed project will assess the evidence for the effectiveness of this form of intervention, which intervention variants are most effective, and for whom these interventions are most effective. The specific aims of the project are to 1) assess the overall effects of brief alcohol interventions on adolescent and young adults' alcohol and other illicit substance use, 2) examine whether the effects of brief interventions are maintained over time, 3) investigate the relationship between intervention effects and participant characteristics (e.g., age, gender, psychiatric comorbidity, baseline substance use), and 4) identify the characteristics of the brief interventions (e.g. dosage, type, setting) that show the largest effects. The proposed project will compile a meta-analytic database of detailed information from the corpus of experimental and quasi-experimental studies examining the effects of brief alcohol interventions for adolescent and young adults. Studies eligible for inclusion will be those involving a brief intervention explicitly intended to prevent or reduce alcohol use for participants age 25 or younger. Detailed information will be extracted from study reports related to general study characteristics (e.g., location, year of publication, methodological design), intervention characteristics (e.g., computerized, group setting), participant characteristics (e.g., age, gender, race/ethnicity, psychiatric comorbidity, prior alcohol and substance use), and the magnitude of the effects on the targeted outcomes. Published and unpublished studies in all languages will be eligible for inclusion. Standardized mean difference effect sizes will be used to represent the alcohol and substance use related outcomes. Random effects main effects and meta-regression models with robust standard errors will be used to estimate intervention effects and the moderating role of participant and intervention characteristics.